1. Field of the Invention
The present invention generally relates to a zoom lens barrel adapted for use in a camera, and more particularly relates to a zoom lens barrel having a reduced lens length, which, accordingly, results in reduced camera thickness when the zoom lens barrel is retracted into camera body to which it is attached.
2. Discussion of Background Information
Recently developed compact cameras have minimized their width and height dimensions to limits which are essentially set by the film size and the camera aperture size. To the contrary, reduction of the thickness of the camera is restricted or limited by the length of the camera lens when retracted into the body of the camera. When retracted, the required length of the lens (hereafter also referred to as the "accommodation length") increases as the displacement of the groups of lenses in the zoom lens increases, resulting in the need to use a longer cam ring to move the lens groups. Thus, if required displacement of the lenses in the lens group is not equal to the desired length of the cam ring, it is possible that even when the lens is retracted, the cam ring will still project outwardly from the camera body, thereby resulting in a relatively large thickness camera.
Thus, one primary object of the present invention is to provide a zoom lens barrel in which the thickness of the camera in which the lens is positioned, when the lens is retracted or accommodated, can be decreased without decreasing the accuracy or precision of movement of the lens.
The present inventor has recognized that one present obstacle or bar to reducing the thickness of the camera is the use of a cam ring which rotates at a fixed axial position to move the lenses in a lens group between a photographing position and a lens accommodating (or retracted) position within a conventional lens barrel. Accordingly, the present invention is at least partially directed to solving the above-noted problem, i.e., it is directed to overcoming and eliminating the above-mentioned obstacle. In other words, the present invention provides a zoom lens structure without using a cam ring which rotates at a fixed axial position.